What is the best board bag to use to keep heat out? I take my board to work sometimes so I can go surfing right afterwards. It is in the car with the windows down 2-3 inches. I’ve heard White is best also that Silver reflective is best . And have been told to leave the Zipper open . This assumes that the bag has a Zipper and is NOT a Sock type deal… What is the “Hot” setup for keeping heat out Thanks, Aloha & Happy 4th
don’t leave it in a hot car, period
The best boardbag to keep the heat out would be some sort of vacuum, but I don’t think that Thermos is making boardbags. The foil/white is to reflect light (well OK infrared), so it only works for radiation. If you leave your board in a car, it really doesn’t matter if its in a board or not – its an oven, give it time and it will cook the inside too. A full day of work is plenty of time – I think the last poster said it best… “don’t leave your board in the car, period.” Btw, I would doubt the zipper being open does anything, air’s going to get in and out just fine… if it didn’t you would find a balloon in your car at the end of a day.
Lash the board (in a bag) underneth the car. Avoid the hot parts. Don’t let anyone see you. Could be quick if you develop some kind of retractable brackets. Just a thought. Rob Olliges
White is the best. Lighter colors are alright too. Foil is not so good.
First, I keep all my boards in reflective silver bags for traveling. I prefer “Destination Surf” bags (I am not affiliated with them in any way) because they are the best construction for the money. Secondly, why don’t you just take the board into work with you? Don’t ever leave it in the car.
I decided to put some effort into testing how to make a surfboard bag that keeps a surfboard cooler in sunny conditions.
My efforts were rewarded with some very clear and plausible results, and a way to improve existing board bags massively for little cost - just paint the top side (or all of it) white.
Although I agree that it is a bad idea to keep a board in a car when parking in the sun, the bag material will still make a big difference when the sun shines directly onto the board through the windows. The entire board will eventually get as hot as the air inside the car, but the parts in direct sun will get much hotter, sooner.
The biggest difference in board temperature due to bag construction occurs when the board is on the car roof, or somewhere else outdoors in direct sunlight.
About a year ago, I decided to turn a surfboard bag inside-out, assuming that the brilliant white liner would reflect light and keep the board cooler. I did not test it properly, and then found weeks later that the board seemed to actually get hotter than with the silvery side on the outside. I turned the bag around again and tried to forgot about it for a year.
Then, I bought a new bag and the guy in the factory shop told me that they sell and recommend bags with the white on the outside because the board stays cooler. I told him that I gained the strong impression that this was not actually true.
He gave me offcuts of the materials that they use to make the bags so I could do some objective testing.
The materials are very similar to most surfboard bags I have seen in shops: A silver-grey woven plastic sheet, a white woven plastic sheet, and clear foam between the two.
I made a bunch of different mini-surfboard-bags by stapling the materials together with an office stapler, and then sealed the sides with duct tape of a similar colour to the outer layer of the mini-bags.
To simulate surfboards, I used galvanised iron braces of about 2mm thickness, bought from a hardware shop. I covered them in sticky tape of varying colours to simulate surfboards of different colours. These metal ‘surfboards’ have the advantage that they will stay hot for a little while and conduct heat very well, so the exposed ends (without sticky tape) let you feel the temperature in the bag very well. I also used an IR thermometer, but it is not required, as the temperature differences are large enough to be felt by hand.
By fitting the galvanised iron surfboards into the mini-bags, objective testing in varying conditions is now possible.
Results from different layering of the surfboard-bag materials:
**The ‘traditional’ surfboard bag with silver/foam/white/surfboard layering is the worst when there is direct sun with little or no wind. **This is probably similar to the situation inside a car, but I have not actually tested inside a car. When it is windy, the heat generated in the silver layer is constantly transported off by the wind, and much less gets into the surfboard.
The ‘inside-out’ board bag with white/foam/silver/surfboard layering is the worst when it is windy and sunny, e.g. on top of a driving car. This is because the wind cannot cool down the layer that gets hot (i.e. the silver layer on the inside). Although a lot of energy is being reflected by the white outside, and the outside feels deceptively cool, the silver layer on the inside absorbs much of the light and consequently heats up. Because of the insulation by the foam, little of this heat is transmitted to the outside, but most of it goes into the surfboard.
Adding an additional layer of white plastic material can make a big difference when the layering is white/silver/foam/white/surfboard, but makes practically no difference when it is layered white/foam/silver/white/surfboard.
The ‘traditional’ mini-bag with additional white plastic on the outside was better than all other bags, including some reflective bubble-wrap insulators I tested.
I concluded that, in order to keep the board cool, the bag must first reflect as much light away as possible, but must also absorb as much as possible of the remaining transmitted light before it penetrates deeper into the bag.** The absorption must occur as close to the outside surface as possible, so that the bags surface heats up rather than it’s inside**, and heat ‘loss’ through convection to the outside is maximised.
From there, the obvious solution was clear: Paint the outside of the bag white. The light absorbing (and consequently heat generating) silver layer cannot get any closer to a reflective layer on the outside than to a painted-on layer. There will always be an air gap between two layers of plastic cloth, causing a bit of insulation. “Painted on reflectivity” should theoretically have better thermal bonding than any other added layer.
I tested this by painting part of a surfboard bag at first, and the temperature difference of the actual surfboard inside it was massive between painted and unpainted areas.
I also painted the ‘traditional’ mini-bag white on one side, to enable objective comparison to the other mini-bags.
Result: The painted bag is far better than all the others (as in: The contents stay much cooler").
The beauty of this is that I don’t need to pay for a new bag with extra layers, but I was able to retro-fit the old bags I have and make them really good with regards to sun blocking.
A further test (with a cherry red surfboard in a real bag) showed that three layers of paint are a little bit better than 2 layers, but not much.
Three layers of white paint onto an old or new surfboard bag will improve the heat blocking ability massively (if it’s the woven silvery type of bag). With massive improvement I mean that the board feels just a bit warmer than ambient air temperature, whereas with the unmodified ‘traditional’ boardbag it would be too hot to touch comfortably.
It remains to be seen how long it takes before the paint starts to flake off, but so far it appears to stick really well.
I rubbed two board bags (one 15 years old, the other 2 months old) with acetone before painting them. I think the paint is Dulux Weathershield matte white, but I’m not entirely certain, it was in a small leftover container. I can probably find the original container if anyone wants to know.
Because of the recent post in this old thread, I’m moving it to general discussion, at least for the time being, since it would likely be missed by a lot of people in the archives folder. Still a timely subject.
Yeah, thanks for reviving the thread from the archives!
I only realised that I had picked some old thread from the archives when I posted the reply to it. I searched the site for relevant threads, in case it had all been covered before, and this one (and one other one also in archives) came up.
yes greg is correct white boardbag is coolest. Take a look at zink oxide…hehehehe
Mr MIK, thanks for that. Here in Florida we fight the heat constantly.
Same here in SE Queensland. Sometimes I can smell the polyester fumes coming out of my 15 year old surfboard when I open the bag on a hot day…not good! But that problem is no more with the painted board bags.
Interesting experiment. Nice study.
Aside: the old “Marijuana Grower’s Guide” recommended using flat/matte white surfaces rather than aluminum foil or silver for light reflection.
That because aluminum stores heat (infra-red) while white paint reflect it.
Maybe mylar or its cheaper version the survival blanket could work for board bags too ?
Did u test survival blanket or multilayer insulation film to get extra protection againt heat ? maybe between the white outer layer and the inside foam ?
Very interesting test indeed ! thx for sharing !
Z.
Heads up ball Huck. Good job. Onya!
I found the paint tin used to paint the surfboard bags against heat: “Dulux Weathershield / Vivid White / Low Sheen”
After about a month of regular usage a few pieces of paint have flaked off. I guess less than 2-3% of the surface area so far.
There have been a few hot days (but no stinking hot ones) and the board was on top of the car, parked in full sun. Every time I checked, the board felt just luke-warm!
I’m confident this bag will keep the board safe from overheating when left outside, and inside the car while driving (but not when parking).
Next step will be to try out paint additives and/or base coats to improve paint adhesion. I have some “Penetrol” left over and once the flaking has gotten bigger, I’ll check if that helps.
Any suggetstions how to iprove paint adhesion to board bags?
The paint has unfortunately not stuck well enough. It began to flake off more and more, leaving a mess in the car and a Haensel and Gretel tail of small white fragments wherever the board bag goes.
I removed the paint with duct tape, a plastic scraper and a vacuum cleaner. The positive result of it so far is that the paint stuck very well to areas that previously had duct tape on it, which has left a little residue which helped adhesion. See around the fin slot in the bag, which I had taped up. The paint is very hard to remove there.
Also, the paint sticks very well to the soft, black plastic nose and the oval logo on the bag, and no matter how much I bend it, it does not crack.
What this means (I hope) is that the paint will stick well with some undercoat.
The bag was covered yesterday with “Penetrol” and is in the 24hr drying period. Then, I’ll paint it again and will let you know how that goes.
Looking forward to hearing how it goes…
'Onya MrMik!
Nice work there with the experiments - incidentally, have you done any experiments with a fin-sock style construction (I usually use one of them) for comparison?
Will be interested to see how the undercoat/better paint adhesion experiment goes; you’ve got me interested in modding a board-bag now 
And good work too to Huck for moving the thread.
Cheers all!